OBRABOTKAMETALLOV Vol. 24 No. 2 2022 TECHNOLOGY Fig. 5. Visualization of oscillation propagation along a plate made of AMg4 alloy in the longitudinal direction (for which the calculation was done), there are transverse bending vibrations that lead to certain rounding of vibration nodes, which is especially prominent in the nodes most distant from the fi xing point in low-amplitude and intermediate conditions. There are also longitudinal vibrations transmitted from the waveguide, the proportion of which increases with increasing power. In high-amplitude conditions, longitudinal vibrations dominate over the others, which, in combination with high amplitude, leads to the powder completely sliding from the plate (the fi rst moments of that process are shown in Fig. 6). Bending vibrations are predominant at 200 W and 350 W, and antinode zones and vibrations nodes are well defi ned on the plates. In low-amplitude conditions, vibrations nodes and antinode zones are less pronounced, since the powder is less displaced from the vibration zone and, accordingly, the node zones are much wider. When measuring the half-wave, its length varies from 19.7 to 21.1 mm, and the vibrations are irregular along the plate width. For example, at the section with the half-wave of 19.7 mm, the antinode is located in the central zone on the one side and along the ends on the other side. In intermediate conditions, the pattern considerably corresponds to the estimate indicators. The vibration zones are very prominent; the distance between vibration nodes is almost the same along the plate length and is 20.8 mm. If the calculation is done using equation (4) for frequency 21,100 Hz, the half-wave length is λB/2 = 21 mm, the error is 1%. The difference of 200 Hz does not play a key role in selecting the welding location since the antinode z one width in this case is more than the nodes and the shift of 0.2 mm does not affect the variation nature in the welding zone. In high-amplitude conditions, vibrations occur along the entire plate length due to the predominating radial component. There are zones of maximum and minimum vibrations, which, by location, correlate with other modes. The plate picture (Fig. 5) shows that the powder on the closer end slides down from the maximum amplitude zone faster than from the minimum zone. An optimal welding location (the bold line in Fig. 5) for low-amplitude and intermediate conditions is 78.5 mm from the left plate end, which is 1 mm longer than the calculated length lw = 77.5 mm. In highamplitude conditions, welding can be done in any place.
RkJQdWJsaXNoZXIy MTk0ODM1